\Header{write.dta}{Write files in Stata binary format}
\keyword{file}{write.dta}
\begin{Description}\relax
Writes the data frame to file in the Stata version 6.0 or 7.0 binary
format.  Does not write matrix variables.\end{Description}
\begin{Usage}
\begin{verbatim}
write.dta(dataframe, file, version = 6,convert.dates=TRUE, tz="GMT",
 convert.factors=c("labels","string","numeric","codes"))
\end{verbatim}
\end{Usage}
\begin{Arguments}
\begin{ldescription}
\item[\code{dataframe}] a data frame.
\item[\code{file}] character string giving filename.
\item[\code{version}] Stata version: 6 and 7 are supported.
\item[\code{convert.dates}] Convert \code{POSIXt} objects to Stata dates?
\item[\code{tz}] timezone for date conversion
\item[\code{convert.factors}] how to handle factors
\end{ldescription}
\end{Arguments}
\begin{Details}\relax
The major differences between Stata versions is that 7.0 allows 32-character
variable names. The \code{abbreviate} function is used to trim long
variables to the permitted length. A warning is given if this is needed and
it is an error for the abbreviated names not to be unique.

The columns in the data frame become variables in the Stata data set.
Missing values are correctly handled.  Optionally, R date/time objects
(\code{POSIXt} classes) are converted into the Stata format. This loses
information -- Stata dates are in days since 1960-1-1.  \code{POSIXct}
objects can be written without conversion but will not be understood as
dates by Stata;  \code{POSIXlt} objects cannot be written without
conversion.

There are four options for handling factors. The default is to use
Stata \code{value labels} for the factor levels.
With \code{convert.factors="string"}, the factor levels are written as
strings. With \code{convert.factors="numeric"} the numeric values
of the levels are written, or \code{NA} if they cannot be coerced to
numeric. Finally, \code{convert.factors="codes"} writes the underlying
integer codes of the factors. This last used to be the only available
method and is provided largely for backwards compatibility.

For Stata 8.0 use \code{version=7} -- the only advantage of Stata 8.0
format is that it can represent multiple different missing value
types, and R doesn't have them.\end{Details}
\begin{Value}
\code{NULL}\end{Value}
\begin{Author}\relax
Thomas Lumley\end{Author}
\begin{References}\relax
Stata 6.0 Users Manual, Stata 7.0 Programming manual, Stata 8.0 online
help describe the file formats.\end{References}
\begin{SeeAlso}\relax
\code{\Link{read.dta}},
\code{\Link{attributes}},
\code{\Link{DateTimeClasses}},
\code{\Link{abbreviate}}\end{SeeAlso}
\begin{Examples}
\begin{ExampleCode}
data(swiss)
write.dta(swiss,swissfile<-tempfile())
read.dta(swissfile)
\end{ExampleCode}
\end{Examples}

